wined3d: Initialize output texcoord .w to 1.0 if needed.

wined3d: Initialize output texcoord .w to 1.0 if needed.

The GL_ARB_vertex_program extension does not define a standard value for
output texture coordinates. This makes problems when using vertex
shaders with fixed function fragment processing because fffp divides the
texture coords by its .w component. This means that gl shaders have to
write to the .w component of texture coords. Direct3D shaders however
do not.